[PATCH v4 2/3] vhost/vsock: discard IOTLB when ACCESS_PLATFORM is cleared

[Jia Jia <physicalmtea@gmail.com>]

vhost_vsock_set_features() leaves the device IOTLB attached when
userspace clears VIRTIO_F_ACCESS_PLATFORM. Descriptors can therefore
continue to use translations installed before the feature change,
including HVAs made stale by a later memory table update.

Use the common vhost helper to detach the device IOTLB before
acknowledging a feature mask without ACCESS_PLATFORM. The helper clears
each virtqueue's IOTLB pointer and metadata cache under its mutex, then
frees the old IOTLB after all virtqueues have dropped their references.

Fixes: e13a6915a03f ("vhost/vsock: add IOTLB API support")
Suggested-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jia Jia <physicalmtea@gmail.com>
---
 drivers/vhost/vsock.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index 9aaab6bb8061..b69c260eaeff 100644
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -863,7 +863,11 @@ static int vhost_vsock_set_features(struct vhost_vsock *vsock, u64 features)
 	if ((features & (1 << VHOST_F_LOG_ALL)) &&
 	    !vhost_log_access_ok(&vsock->dev)) {
 		goto err;
 	}
 
+	if (!(features & (1ULL << VIRTIO_F_ACCESS_PLATFORM)) &&
+	    vsock->dev.iotlb)
+		vhost_clear_device_iotlb(&vsock->dev);
+
 	if ((features & (1ULL << VIRTIO_F_ACCESS_PLATFORM))) {
 		if (vhost_init_device_iotlb(&vsock->dev))
 			goto err;
-- 
2.34.1